【Tomcat9源码分析】Container、Pipeline和Vavle设计

转载请注明出处：http://blog.csdn.net/linxdcn/article/details/73800100

1 概述

如果你对Tomcat的整个框架、组件、请求流程不熟悉，建议你先阅读以下3篇Tomcat概述性的文章，再来看本篇文章：

【Tomcat9源码分析】组件与框架概述
【Tomcat9源码分析】生命周期、启动、停止概述
【Tomcat9源码分析】请求过程概述

Container是Tomcat中很重要的容器，主要包含Engine、Host、Context和Wrapper，其采用了责任链的设计模式，来处理一次请求。

2 Container分析

Container是一个接口，Tomcat提供了ContainerBase作为其实现的基类。

2.1 字段

public abstract class ContainerBase implements Container {// 子容器protected final HashMap<String, Container> children = new HashMap<>();// 监听事件protected final List<ContainerListener> listeners = new CopyOnWriteArrayList<>();// Container对应的Pipelineprotected final Pipeline pipeline = new StandardPipeline(this);// 领域对象private volatile Realm realm = null;
}

2.2 启动

public abstract class ContainerBase implements Container {@Overrideprotected synchronized void startInternal() throws LifecycleException {// 1 启动领域对象Realm realm = getRealmInternal();if (realm instanceof Lifecycle) {((Lifecycle) realm).start();}// 2 启动子容器Container children[] = findChildren();List<Future<Void>> results = new ArrayList<>();for (int i = 0; i < children.length; i++) {results.add(startStopExecutor.submit(new StartChild(children[i])));}// 3 启动Pipelineif (pipeline instanceof Lifecycle)((Lifecycle) pipeline).start();// 4 设置状态，启动本线程setState(LifecycleState.STARTING);threadStart();}
}

1. 启动领域对象
2. 启动子容器
3. 启动Pipeline
4. 设置状态，启动本线程

3 Pipeline分析

Pipeline是一个接口，其实现类是StandardPipeline。

public class StandardPipeline extends LifecycleBase implements Pipeline {// 基础阀门protected Valve basic = null;// 关联的容器protected Container container = null;// 第一个阀门protected Valve first = null;@Overrideprotected synchronized void startInternal() throws LifecycleException {Valve current = first;if (current == null) {current = basic;}// 依次启动所有Value，Value是一个链表结构while (current != null) {if (current instanceof Lifecycle)((Lifecycle) current).start();current = current.getNext();}setState(LifecycleState.STARTING);}
}

4 Valve分析

Valve是一个接口，其基本实现的BaseValve类。

public abstract class ValveBase extends LifecycleMBeanBase implements Contained, Valve {// 关联的Containerprotected Container container = null;// 下一个Valveprotected Valve next = null;@Overridepublic Container getContainer() {return container;}// 初始化@Overrideprotected void initInternal() throws LifecycleException {super.initInternal();containerLog = getContainer().getLogger();}// 启动@Overrideprotected synchronized void startInternal() throws LifecycleException {setState(LifecycleState.STARTING);}
}

5 几个重要的Valve

5.1 StandardEngineValve

final class StandardEngineValve extends ValveBase {public final void invoke(Request request, Response response)throws IOException, ServletException {// 1 由request获取hostHost host = request.getHost();if (host == null) {// ...省略return;}// 2 调用host的pipeline的vavlehost.getPipeline().getFirst().invoke(request, response);}
}

1. 根据request定位到可以处理的host对象
2. 依次调用host里的pipeline上的valve

5.2 StandardEngineValve

final class StandardHostValve extends ValveBase {public final void invoke(Request request, Response response)throws IOException, ServletException {// 1 由request获取contextContext context = request.getContext();try {// 2 调用context里的pipeline上的valvecontext.getPipeline().getFirst().invoke(request, response);// response已经返回response.setSuspended(false);Throwable t = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);// 3 如果有错误，重定向到错误页if (response.isErrorReportRequired()) {if (t != null) {throwable(request, response, t);} else {status(request, response);}}} }
}

1. 由request获取context
2. 调用context里的pipeline上的valve
3. 如果有错误，重定向到错误页

5.3 StandardContextValve

final class StandardContextValve extends ValveBase {@Overridepublic final void invoke(Request request, Response response)throws IOException, ServletException {// 由request获取wrapperWrapper wrapper = request.getWrapper();// ...省略// 调用wrapper里的pipeline上的valvewrapper.getPipeline().getFirst().invoke(request, response);}
}

1. 由request获取wrapper
2. 调用wrapper里的pipeline上的valve

5.4 StandardWrapperValve

final class StandardWrapperValve extends ValveBase {public final void invoke(Request request, Response response)throws IOException, ServletException {// 1 获取wrapper, contextStandardWrapper wrapper = (StandardWrapper) getContainer();Servlet servlet = null;Context context = (Context) wrapper.getParent();// 2 加载servlettry {if (!unavailable) {servlet = wrapper.allocate();}} // ...省略catch// 3 新建一个 filter 链表ApplicationFilterChain filterChain =ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);// servlet会放在 filter 链表最后，并且最后会调用servlet的service方法try {if ((servlet != null) && (filterChain != null)) {// Swallow output if neededif (context.getSwallowOutput()) {// 4 调用 filter 链表上的 doFilterfilterChain.doFilter(request.getRequest(),response.getResponse());}} } // ...省略catch}
}

1. 获取wrapper, context
2. 加载servlet
3. 新建一个 filter 链表，servlet会放在 filter 链表最后，并且最后会调用servlet的service方法
4. 调用 filter 链表上的 doFilter

5 总结

转载请注明出处：http://blog.csdn.net/linxdcn/article/details/73800100